blackberry.com says 128gb, and on amazon.com a lot of the Z30's say 64gb. Which one is it?

Well put it this way. When the Blackberry z30 launched it only supported 64gb of expandable storage. Buut the size of the expandable store is dependent on software and not hardware. So if you update your OS to 10.3.2 in theory it should support 200gb I personally tried a 200gb micro SD inside my Leap and it seemed to work fine